This invention relates to an output control apparatus, for a vehicle, which rapidly reduces driving torque of an engine according to an amount of slippage of the driving wheels, hereinafter referred to as slip amount, occurring during acceleration or the like, of the vehicle, thereby ensuring safe running of the vehicle.
When the road surface condition abruptly changes during operation of a vehicle, or when a vehicle is operating on a slippery road with a low frictional coefficient such as a road covered with snow or a frozen road, the driving wheels may often skid.
In such a case, it is difficult for even a skilled driver to adjust the amount of pressure applied to an acceleration pedal and delicately control the engine output to prevent the driving wheels from skidding.
To prevent this, an output control apparatus can be used which detects a skidding condition of the driving wheels. When skidding of the driving wheels occurs, the output control apparatus forcibly reduces the output of the engine independent of the amount of pressure applied to the accelerator pedal by the driver. Further, an apparatus is proposed which allows a selectable operating mode using the output control apparatus, or a normal operating mode, in which the output of the engine is controlled according to the amount of pressure applied to the accelerator pedal, selectable by the driver as necessary.
As an output control method according to this concept, an apparatus is known which detects, for example, a rotation speed of the driving wheels and a rotation speed of the driven wheels. It regards a difference in the rotation speed between the driving and the driven wheels as a slip amount. It then sets a target driving torque according to the slip amount and the operating condition of the vehicle, and controls the throttle valve opening and ignition timing so that the driving torque of the engine is that of the target driving torque.
In a prior art output control apparatus like this, when a reference driving torque of the engine is set according to the traveling speed of the vehicle, the lower peripheral speed of the right and left driven wheels is adopted as a traveling speed of the vehicle, and the reference driving torque is set according to this speed.
In a prior art output control apparatus of a type in which a reference driving torque is set according to changes in vehicle body acceleration, a target driving torque of the engine is set according to the reference driving torque and the slip amount of the driving wheels. The driving torque of the engine is controlled so that the driving torque of the engine is the target driving torque. Since the vehicle body acceleration tends to decrease during a speed shift, the reference driving torque is corrected to a smaller value, and an acceleration feeling, occurring immediately after completion of speed shift, tends to be deteriorated.
In particular, under a condition where the driving torque of the engine is decreased, independent of the driver's manipulation, since, of course the target driving torque of the engine is decreased, an acceleration occurring feeling immediately after completion of a speed shift is almost lost, with the vehicle arriving at a stalling condition.